This section is intended to introduce the reader to various aspects of art that may be related to aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Flat panel displays are incorporated into an increasing number of products, including computer monitors, televisions, cellular phones, personal digital assistants (PDA's), instrumentation, monitoring devices, and the like. Flat panel displays often include liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, and liquid plasma displays. These and other display systems often incorporate micro-electro-mechanical systems (MEMS) within the display to provide a variety of functions including shuttering light to generate images.
Some display systems include a slab waveguide (e.g., a light guide) configured to distribute light to various regions of the display. Light is injected into the waveguide and is reflected within the waveguide in accordance with the principle of total internal reflection (TIR). Totally internal reflected light within the waveguide, referred to as “TIR light,” is emitted from the waveguide when the internal reflection is frustrated in accordance with the principle of frustrated total internal reflection (FTIR). For instance, total internal reflection occurring at a given region of the waveguide, such as the location of an individual pixel, can be frustrated to eject light from the waveguide at that region. One example of such a FTIR display is a Time Multiplexed Optical Shutter (TMOS) flat panel color display system, wherein MEMS structures are used to selectively control the frustration of TIR light at localized regions (i.e., pixel regions). In one MEMS-based structure, TIR light is frustrated by propelling an optically-suitable material, for example a deformable membrane layer, into contact or near-contact with a surface of the waveguide to couple light out of the waveguide and, thus, create an active region where light is ejected. Accordingly, the active region may include the deformable membrane layer disposed in contact or in near-contact with the display surface of the waveguide, such that TIR light is frustrated and directed out of the waveguide at the active region (i.e., an “ON” pixel). An inactive region generally includes the deformable membrane layer sufficiently displaced from the waveguide by a gap such that evanescent coupling across the gap is negligible, and light is not directed out of the waveguide, but is instead internally reflected into the waveguide at the inactive region (i.e., an “OFF” pixel) due to TIR arising at that surface according to the laws of optics. In a display system, a rectangular array of such MEMS-based regions may be fabricated upon a surface of the waveguide to provide an array of pixels, wherein each pixel is capable of selectively transmitting light out of the waveguide via FTIR. In other words, each MEMs-based region may be selectively switched between active and inactive states, corresponding to ON and OFF states, respectively, of a single pixel. The pixels in an ON state are capable of transmitting light out of the waveguide that can be viewed as an image. The aggregated MEMS-based regions function as a video display capable of color image generation, usually by exploiting field sequential color (e.g., sequentially generating red, green, and blue components of an image) and pulse width modulation techniques. The display systems disclosed in U.S. Pat. No. 5,319,491 and in U.S. Pat. No. 7,092,142, which are herein incorporated by reference in their entirety, are representative of FTIR-based MEMS devices and illustrate the fundamental principles of such devices.
MEMS-based systems, including flat panel displays that exploit the principle of frustrated total internal reflection (FTIR) to induce the emission of light from the system, may need to satisfy certain physical criteria to function properly. For instance, the MEMS devices may have a certain operational voltage level and consume a given power. However, due to the high density of MEMS devices being driven on high resolution display systems in use today, it is desirable to reduce the power consumption of such display systems by any means possible, since excessive power dissipation can turn a competitive display architecture into an untenable design. It would be an improvement in the art to provide an apparatus and method for reducing pixel operational voltage in MEMS-based optical displays.